Parachute Cam and Polaron G1

This weekend we a had a really good launch day. The weather was perfect and the rockets behaved themselves. During some unrelated test flights we took the opportunity to mount one of the tiny MD-80 cameras in the center of the parachute looking down.

Although quite a bit shaky, the video did give us a different perspective on the rocket in flight. The full launch report including photos and a highlights video is available here:

http://www.aircommandrockets.com/day93.htm

The update also includes the test flights of the fiberglass Polaron G1 rocket. On the second flight we flew it at 230psi to 751' (229m) which was our highest (by 5 meters) single stage flight.

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Williams "Wildfire" Westernationals 2010

This weekend I took a break from water rocket development and headed over to Perth to attend the Williams "Wildfire" Westernationals 2010.

What an awesome experience it was to see a lot of high power rockets go up. It was great to finally meet a lot of the people in person from the Australian Rocketry forum as well. They are great bunch of guys too. A big thank you goes to Scoop and Mel and all those who helped organise and cater the event.

Congratulations to all those who did their L1, L2 and L3 certifications.

Here are some pictures from the event:

http://ausrocketry.com/forum/viewtopic.php?f=37&t=2189


Very strong the dark side is ......

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Water Rocket Labs

Well finally after many delays and procrastinations, I've uploaded the website extension. Originally it was going to be a separate entity, but I have decided to just make it a sub-section of the new site. This also makes it logistically easier to administer.

"Water Rocket Labs" was developed to help water rocketeers make better decisions about building their rockets. The site provides data and analysis about various aspects of water rocketry including materials and their performance.

The focus is not only on the data itself but also on the procedures and test equipment used to obtain the data. This allows others to follow the same procedures and compare their results against the data presented at the labs. The data is cross linked to the experiments, test procedures and test equipment used to obtain them.

Some of the experiments included in the site have been published before on our main site, however, there is a range of experiments we had not published before. With the previously published results I have trimmed them down only to the relevant information.

We will continue to update our regular site with launch reports, articles, construction details etc, but all new science or engineering results will go into the Labs section.

There are around 80 pages of information in the extension. Some sections are still sparsely populated, but we now have the framework to add more data as we obtain it.

Here it is: http://www.aircommandrockets.com/labs/index.htm

We invite people to submit their data to the Labs that will hopefully help others make better decisions about building water rockets.

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Water Rocket Launcher Article

Over the last month I've slowly been putting together an article to help explain the range of different launcher design options rocketeers have when building their own.

The article is available here:

http://www.aircommandrockets.com/rocket_launcher.htm

Along similar lines as the recovery guide I've tried to include lots of links to examples showing how the different components have been implemented by the water rocket community.
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Moving Main Website

I've been putting it off for long enough, so this weekend I have started relocating our main website. Up until now we have been hosting it on a free 50Mb partition we get with our ISP. The problem was that we were running out of room, well for quite a while now actually, so a lot of the actual images had to be hosted elsewhere.

To expand the 50Mb partition just wasn't possible with this ISP without signing up for actual 'hosting' where they wanted another $50 setup fee and then an extra $110/year for 100Mb of space. That was just ridiculous. So we have gone with an alternative hosting company where we only pay $70/year for 10Gb of space.

The usual domain: http://home.people.net.au/~aircommand/ will be replaced with http://www.AirCommandRockets.com/ . We've had the AirCommandRockets.com domain registered for quite a while but it was getting forwarded to the people telecom site.

I will be replacing the people telecom pages soon with forwarding pages to the new site, and eventually remove them completely. If you have links with http://home.people.net.au/~aircommand they can simply be replaced with http://www.AirCommandRockets.com as all the underlying website structure remains the same.

The AirCommandRockets.com site is now live but there may be a number of disruptions over the next week or so.

The extra space will allow us to upload the website extension we have been working on and have had to put on hold until we had more space. We'll also now be able to add extra features to the site, that weren't possible before.



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Testing beyond 300psi and old videos

This week dad set up new test equipment for us to use so that we can test beyond 300psi. Which is what our high pressure test panel went up to. We now have test capability up to around 800psi, though we would need to replace the air hose with a high pressure one for the upper range. We mostly wanted to see at what pressure the fiberglass bottles will fail so that we know what the safe launch pressure is.

We now have a nice giant pressure gauge which makes it easy to see.... even by those at the back of the classroom. :)

As we look to upgrade Acceleron V to higher pressures we have to check the individual components to see if they will be up to the job. Here dad was testing the thin plastic tubing we are using for the sustainer air supply line. It goes between the baseplate release mechanism and the staging mechanism with a non-return valve along the way. It says on the side it is rated to 50psi operational pressure. We have been pressurising it to 130psi (having previously tested it to 180psi) With our rocket pressures now nearing 250psi, this was always likely to be a weak point ......

Here it is still holding around 630psi! ....If you notice in the background, the whole experiment is now covered with a pile of concrete pavers.

Old Videos

About a week ago we noticed that some of the older videos on our website weren't playing. I'm not sure how long it's been like that. These mostly covered flight days 1 to 55. It turns out MySpace changed how videos are embedded and that broke all the existing embeded URLs. *sheesh*

So tonight I've gone back and fixed up all the embedding code to reflect how MySpace wants to do it .... until next time. We've stopped using MySpace around day 55 for our videos and now almost exclusively upload to YouTube.

I must go back and check over other broken links on the website as some things have disappeared. I try to fix them as I come across them, but there are always new ones. If people come across broken links please let me know and I'll try to fix them if possible.
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Fiberglass rocket launch report

I've updated our main website with the latest launch report on the flights of one of the fiberglass rockets. The update is available here:

http://www.AirCommandRockets.com/day92.htm

It includes photos and a highlights video from the day. The small rocket that was launched at 245psi managed to get up to 744' (226m). We thought that was pretty reasonable considering it was slightly bent, used a small 9mm nozzle, and no launch tube. .... right... can't sit around here typing .... must get back to the workshop :) ....

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Great Photos from Acceleron V flights

Andrew Eltobaji from NSWRA took some great photos of our 2 stage rocket from a month ago. He definitely has great skill in catching fast moving rockets in action.

See some of his other pyro rocket photos here: http://s278.photobucket.com/albums/kk99/elta100/ and click on the NSWRA folders on the left side.

Here are some of his photos from the day. I have included them here in their almost full resolution. (Blogger will not let me upload the full resolution.)  Be sure to click on the photos so you can zoom in and get a good look at the detail. I wish I could take good photos like that!



Flight #2

I'm actually not that close to the rocket ... telephoto lenses are great!

It looks like the red booster is a little late in starting its air pulse.

Blue food colouring in the water is a great way to contrast against the white clouds

Secondary (backup) parachute is being deployed.

Coming in for a gentle landing

Flight #1

Good laminar flow from all of the nozzles during the booster's water phase.

Without the blue colouring, things are less messy on the ground.

Rocket is suspended sideways to cause extra drag and land more gently.

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Fiberglass rocket flights

This week has been a very busy week in trying to get a couple of fiberglass rockets ready for today's Doonside launch. We ended up flying the smaller one four times, with some failures as well as some very good and promising results. There was a very strong wind at the launch site and so we decided not to launch the bigger rocket. We ended up launching the last rocket at 245psi - our highest launch pressure to date.

I'm in the process of putting together a launch day report again, which should hopefully be available in the next couple of days.
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Fiberglass pressure test results

We have now tested a number of glass reinforced spliced-pairs of bottles. The results so far look quite promising in improving the performance of our rockets. The extra weight of the reinforcing requires an extra 30psi to compensate, but the much higher launch pressure should raise the altitude considerably.

Next we need to assemble these into a proper rocket and pressure test it for leaks.

The full update including performance simulations is available here:
http://www.AirCommandRockets.com/day91.htm

The update also includes a progress build on our first MPR pyro rocket.
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Fiberglassing pressure vessels

Yesterday we had our first go at fiber-glassing some bottles in order to be able to safely increase the launch pressure. We wrapped one spliced pair with a single layer of glass and the other with a double wrap.

The bottle on the left has a single layer and the one on the right is double layer. The bottles are only spliced with Sikaflex 11FC glue for an air tight seal. We are going to give the splices a week to fully cure before hydro testing them to destruction. I'll post the results of these tests when they are available.

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Acceleron V flights Update and Video

I have finished doing the launch report for this weekend's 2 stage flights. The update is available here:

http://www.AirCommandRockets.com/day90.htm

The update includes photos, altimeter plots, flight event time lines as well as a highlights video.

Here is a view of the Doonside launch field.

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New personal records

We had a great launch day today at Doonside. We finally got the Acceleron V rocket with Axion IVb sustainer flying properly. ...ie. upwards and also not into pieces. We launched the pair twice on the day at 120 psi.

 Acceleron V taking off on its second flight.

The sustainer reached 787' (239m) on the first flight and 810' (246m) on the second flight. Our previous highest altitude was 637' (194m). We also set our longest water rocket flight time at 1:00 min.We were hoping to break the 200m mark with this flight, and got the 800' mark as well. We are going to have a good look at the data from these flights and see where we can make further improvements.

I will be putting together a main website update over the next few days with more details, video and photos from day.

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Comparing real world data to simulator data

We've uploaded the flight day 89 launch report to our main website here:

http://www.AirCommandRockets.com/day89.htm

The update includes pictures and video from the launch day as well as a comparison of acceleration data from a couple of flights and 3 water rocket simulators.

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Doonside launch

Over the past couple of weeks we have been continuing to build rockets, although a little slower due to other non-rocket related commitments.

This weekend we flew a couple of different experiments at Doonside. We wanted to flight qualify the Acceleron V sustainer testing the jet foaming tornado coupling insert in the process.

We also flew three test flights with Craig's pyro rocket flight computer. It didn't control deployment but was along for the ride to gather flight data. The data from these flights and simulation results for comparison will be published in the next main site update.

I'm still in the process of writing up the full launch report which will take at least a couple more days.

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Dual Deployment

On Saturday we had a good launch day at Doonside. We tested a dual deploy mechanism on a couple of smaller rockets, and even managed to explode one on the pad. We also test flew the MD-80 clone camera on 3 of the flights.

The full update is available here:
http://www.AirCommandRockets.com/day88.htm

The update includes, videos of both water and pyro action from the day. There are also a couple of updates on some of the other things we have been working on.

Photo: Andrew E.

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Acceleron V rebuild

We've made good progress this week in getting Acceleron V back on the launch pad. Early in the week we tested the new narrow nozzle seals to make sure they will hold up to the pressure. This was also a pressure test of the booster side of the launcher. During assembly we noticed that one of the nozzle seals was distorting too much when the bottle was tightened. So dad machined up a new nozzle seal cutter that was a little wider and we made 3 new nozzle seals out of harder rubber. These worked well during assembly and in the pressure test.

Pressure testing the new nozzle seals. You can see the fog in the upper bottles as we let the pressure out.

On Friday we pressure tested the sustainer release mechanism and air supply. During the test we noticed that there was a very minor leak (1 or 2 drops per second) in the release head. On closer inspection it looked like there were a couple of small vertical grooves in the o-ring seat. So we spent today replacing the Gardena release mechanism with a new one. We are letting the epoxy fully cure before doing another test.

We spent the rest of today re-assembling Acceleron back to its normal configuration,.

Attaching the fins with the use of a fin alignment jig.

There are still lots of little jobs to do on the rocket, but it's good to see it back together again. We will do an integration pressure check to around 60psi to make sure there are no leaks in the Tornado couplings without putting too much stress on the entire rocket.

Next major milestones include a re-assembly of the sustainer. Depending on our progress schedule we may fly it at this weeks NSWRA launch day to flight qualify it before it gets used with the Acceleron booster.
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Pressure tests

After a week of curing, yesterday dad hydro tested 5 of the new splices to go into Acceleron V. These ones had a slightly narrower sleeve than the previous 4 for ease of manufacture. The results were all good with the test having the splices hold 140psi for 30 seconds. There were no leaks and no visible stress marks.

I'm happy with the yield rate so far for these splices. We haven't had any leaks in the 10 we have made to date. I'm sure there will be the occasional one that will leak or fail, but so far it's a good start.

We now have enough of the splices to put Acceleron V back together again. We will do a nozzle seal check next by placing the lowest bottles with nozzles on the launcher held down via the baseplate and checking to make sure the new nozzle seals are good. We won't need to remove the nozzles after the test.

Because the new pressure switch is only a SPST type, we can't wire it directly to an LED like last time to tell us that enough pressure is in the booster. When this LED was ON (@~20psi) we knew the switch was activated and the flight computer was safe to arm. I'm going to update the software in the primary computer to give us a pressure switch status indication on the LED display so that we can tell when it's safe to arm it. Although we could get it to arm automatically when the pressure switch activates, I still prefer to keep the human-in-the-loop for these kinds of things in case we need to abort the launch.
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Flight day and progress

Last week we went to the NSWRA launch day as we wanted to see the egg lofting competition. We weren't going to fly rockets on the day as Acceleron V has been taking up all spare time, but we did put a couple of small ones in the back of the car just in case. We ended up flying a couple of them during the day. I'm putting together a couple of videos at the moment. One is just a short one from the day showing the flights, but the cloud cover made it difficult to get a good shot against the white clouds. The other video is a discussion about some of the components going into Acceleron V booster.

I'll do a short write-up over the next couple of days. Otherwise it's been a continuation with splicing all the bottles.

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1st splice phase complete

Last night we finished gluing the 12 x 2L and 10 x 1.25L spliced pairs with the Sikaflex glue. The splices went together quite quickly, but preparation took a bit of time because it included heat shrinking the bottles, curling the edges, cleaning with alcohol, sanding and applying the masking tape before gluing could begin.

 Next we need to glue on the outer sleeves with PL and then re-enforce them with the other bottles and glass strapping tape. This should happen over the next few days.

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Splicing, splicing and more splicing

With the recent flights out of the way, we are now solely concentrating on getting Acceleron V back in the air. The first thing we need to do is make up more of the new spliced pairs we have been testing. Over the last 3 months we have been slowly collecting bottles from friends and family, so now we have some 70 odd bottles ready to splice.

We will be making up a stock pile of spliced pairs, not just for Acceleron V but for other rockets. We are also going to have a go with the 1.25 bottles at making spliced-quads. 4 bottles spliced together with a neck at either end. This will give us ~4L in a 90mm diameter body. We'll still be able to join them using Tornado couplings, but they should give us a little more performance. If they go well in tests we may use them on Acceleron V's sustainer.

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In-line deployment mechanism

We've updated our main website with the rest of the flight day report from 10th January 2010.

http://www.AirCommandRockets.com/day86.htm

The update shows more details of the lightweight deployment mechanism we have been recently testing. The Tomy timer version weighs 35grams.

The update also includes a highlights video from the day.

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Mercury Switch Experiment Results

We've completed the write-up for the experiment. The full results are available here:

http://www.AirCommandRockets.com/day85.htm

I was surprised by some of the results while others were as expected. Included are pictures, altimeter graphs and a video of the entire experiment.

I was going to include the full flight day report from Sunday in this update, but because it was kind of long anyway, I decided to separate it. The rest of the flight report will be done over the next few days including a description of the lightweight deployment mechanism and a video of how it works.


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Flight MicroLab - Mercury Switch Experiment

One of the things we want to fly this weekend at Doonside is a small science experiment. The main intention is to demonstrate how mercury switches behave during flight. It is a very common question we get asked all the time. "Why not use a mercury switch to detect when the rocket tips over at apogee?" ... it's a reasonable question since the system works well on the ground.

I thought video taping what they actually do in flight should give people a better understanding why they don't work the way they think they should.

Experiment setup:

There is a small digital video camera looking through a lens at a set of three mercury switches. Two are mounted the way people would typically mount them and the other is mounted upside down. They are wired to an LED each so you can see when in flight they actually activate. There is also a light source (white LED) above them so the mercury can be clearly seen. There is also a barometric recording altimeter mounted on the side to correlate the activation timing of the switches vs altitude/speed.

The parachute will be set to deploy later than normal so we can see what happens through apogee and somewhat beyond. After we have flown it I'll post the results to our regular website again.



Here is the MicroLab before being installed in the rocket. The rocket will be a Polaron style rocket of around 9.5L. capacity. The rocket is made up of the old Acceleron V bottles so we will be launching it at only about 110psi.

Front view

Back view with power turned on

View from inside the experiment

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Preparation for launch day

Happy new year! Having had a nice break over the Christmas and new year we are back in full swing with rocket development.

The next launch opportunity is on Jan 10, so we are working to have a number of rockets ready for the day. One of the rockets we'll be testing is the new smaller and lighter deployment mechanism. It weighs less than half of the one we have been using.We'll test it on a small rocket first and then if things go well, we'll extend the rocket and try it at higher speeds and altitude.

We are also preparing a Polaron style rocket that will do a number of in-flight experiments.

Dad has finished upgrading one of our air control panels which will now be able to deliver two different pressures each up to 300psi. This will be useful for the upcoming re-enforced rockets to be launched at higher pressures.

Some goals for 2010 include:
- Getting Acceleron V back in the air on a number of flights, and pushing it to its limits.
- Finishing off V1.7 of the flight computer.
- Getting the website extension completed.
- Higher pressure launches.
- More instructional videos and construction instructions.


We hope everyone has many successful flights with their rockets this year.
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Pressure switch testing

I've posted the results of the pressure switch tests here:

http://www.AirCommandRockets.com/day84.htm



The switch seems to be working well so now it's onto finishing the rest of the spliced pairs and getting Acceleron V re-assembled.

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Acceleron V pressure switch

This weekend dad and I worked on the Acceleron V pressure switch. On Acceleron's last flight it did not look like the pressure switch(TDD2) worked properly, and the pressure switch(TDD) we were using before on the earlier Accelerons had been somewhat leaky.

The pressure switch is used by the primary flight computer to initiate the staging of the second stage when the booster stops producing thrust.

So we set out to try to make a more reliable one. (I think this is our 5th attempt at a simple and reliable pressure switch). In the photo below is the prototype. The hose clamps are only temporary for the first pressure tests. Also the cut off bottle neck at the end of the switch is only temporary to support the clamp.

We pressure tested the activation pressure and it was around 30 psi. That means that the switch will activate when pressure falls below 30 psi. This is a good value because the flight computer can delay the staging a little bit until the pressure is around zero.

We ran several low pressure cycles to test how well it activates. And the results were always repeatable. We are now gluing it together properly, removing the hose clamps, and when the glue has dried, we will test the switch to full operational pressure to make sure it can still hold up at the higher pressures.

I would also like to set up one of the booster segments on the thrust stand and simulate a launch with the correct amount of water and pressure. The segment will be fitted with the pressure switch so that we can see when the switch activates in relation to the thrust curve. This should allow us to then calibrate the small staging delay for the primary flight computer.

Once the pressure switch is fully tested, I'll do a full write up of how it works on the main website, but it is simple enough for most people to build.

Acceleron V has also been completely stripped down so we can start replacing the bottles with the new spliced pairs.

Deployment Mechanism development

We have also been working on a new deployment mechanism that uses in-line parachute deployment. The main criteria for this is to reduce the weight. Currently the standard nosecone and side-deployment mechanism we are using on a 90mm bottle weighs around 138 grams without the parachute, but it does include all the mechanical hardware, electronics and battery.

The new nosecone and deployment mechanism currently weigh 37 grams (including a servo motor) with the electronics and battery still to be added. The new electronics (FC V1.7) and battery will add about 20 more grams, so all together the entire nosecone should be around 60grams. The design also allows for potentially large parachutes and is also around 30% shorter than our existing designs.

When we've had a chance to test fly it a number of times, I'll again post full details.
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Day 83 Update

I've posted the flight day report from Doonside on our main website here:

http://www.AirCommandRockets.com/day83.htm

It includes a highlights video and photos from the day as well.

I've also updated the flight day report with findings from last night when I was pulling the rockets apart to give them a clean. (see the Update section) It turns out we had some heat distortion issues that we didn't know about on the day. The Polaron VII rocket also flew with a missing o-ring in one of the Tornado couplings!

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Flight testing new splices

Well it's been quite a while since the last update, but rocket development has been continuing although a little slower due to the holiday season coming up. Today we went out to Doonside to test launch the new spliced pairs to see how they behave under flight and landing conditions, as well as sitting in the sun for a while.

The rocket used all 4 spliced pairs previously tested to 140 psi. The rocket was launched a couple of times at 130psi, and the splices held out well without any significant issues. 5 more of these will now be made and fitted to Acceleron V.

I am doing a write up of the whole day along with a few other foam and flour flights we did on the day. I'll post photos and a highlights video in the next few days.

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Keeping neighbours happy

This weekend we were going to do burst pressure tests on a range of bottles, but blowing up bottles in one's back yard isn't something to get your neighbours excited about. We are always looking for ways to lower the noise during these tests. Having the bottle full of water greatly reduces the noise, but a little bit of air can enter the bottle as it expands and so the resultant explosion can still be very loud.

Sound suppression attempt #1:
We filled the bottle with water, and then placed the whole bottle in a small plastic bathtub, filled it full of water, covered the bottle underwater with a towel and held it down with two bricks. ....
Result: Big boom, tub split in half, lawn received a healthy watering.

Sound suppression attempt #2:

So we drove over to dad's house, filled the next bottle with water and suspended it about 1/2m below the water in the concrete in-ground swimming pool.

Result: Quieter boom but what was amazing was the fact you could feel the concrete shake under your feet with the boom! This was a bottle full of water with about 100mL of air in a large pool and it burst at ~160psi. The slow-mo video standing on a tripod on the side of the pool shows the blur as the shockwave hits shortly later followed by tiny ripples on the surface doing interference patterns for about 1-2 seconds. Obviously the shockwave travelled through the water and echoed around the pool. .... WAY COOOL! ... but not the objective. Could the shock wave damage the pool? Unlikely, but we didn't want to take too many more chances.Tiny ripples on the water are the sound waves bouncing around in the pool

Sound suppression attempt #3:
Dad brought out an old SCUBA cylinder with the bottom cut off. This aluminium tank has a wall thickness of about 1cm, and so we place the bottle in it, stuffed old rags in the hole, placed it up against a rock wall, put a bench, lead weights and seat against it to stop the tank from flying in the other direction, wrapped the tank in two layers of foam and burst the bottle ....
Result: A barely audible thud.
Subsequent tests showed that you really only needed the rags in the end of the tank to suppress pretty much all the noise. There was no need for the foam wrap, or weights to hold the tank down.

Putting the bottle in the SCUBA cylinder

Stuffing in rags to suppress the sound.

Tank is under two layers of foam and bench with weights is meant to stop the tank from flying away.

In the end 9 bottles were blown up, and the neighbours didn't complain one bit.
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So far so good ....

During the week we made up four new spliced-pairs of 2L bottles. Each has a capacity of around 3.15L. The splicing and reinforcing technique seems to be working well so far. The Sikaflex is doing its job sealing the splices.

Today they were all pressure tested to 140psi without any leaks, and the bottles and tape showed no stress marks. We are very happy about that. Having a good yield rate means we can produce more of these with less bottles.


Now they will all be assembled into a Polaron type rocket. The initial target launch pressure will be 130psi with a 15mm nozzle. While we are building this rocket we will continue to make up more spliced pairs for the rest of Acceleron. Some of these will also be converted into boosters.


I think I have an approach too now for the pressure switch, so I'll be doing some prototype work on that soon.
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Investigating water behaviour in flight

At Doonside this weekend we flew the Axion rocket again 3 times with a camera on the boom to try and get a better shot of what is happening in the lowest bottle in flight. We used food colouring to enhance the contrast and no foaming agent this time. We also painted the fins a neutral gray to prevent the auto-iris on the camera making everything else too dark.

The full launch report is available here: http://home. people.net. au/~aircommand/ day82.htm


Acceleron V

Since a few people have now asked about when Acceleron V is going to fly again, I might as well do an update. We are in the process of getting Acceleron V back in the air. There were a couple of issues that we really wanted to solve before trying again. The number one priority is getting the spliced pairs reliable enough to be able to launch with them and not worrying about being very close to the burst limit. The last explosion showed that the spliced pairs just weren't there yet. Even though they were tested to 130psi, they were obviously close to that pressure. Although we could fly the rocket at lower pressure, the rocket's flight envelope was really not designed for anything lower than 110psi. Ideally the rocket needs 130-140psi.

The need for stronger spliced pairs is the reason we have been doing the splice tests recently. If further tests with the new splice technique continue to go well, we are hoping to replace the existing spliced pairs with the new ones on the rocket. We have 4 new spliced pairs curing at the moment and we will hydro test them to 140psi. We will then make a Polaron style rocket and test fly them at 130psi. If the spliced pairs perform well in real life situations then we will make up more to replace those on Acceleron V.

The other issue is the pressure switch. We want to have a reliable pressure switch to detect burnout. The pressure switch we used on the first flight just wasn't reliable enough, and the old pressure switch (TDD) leaks a little. When these issues are resolved, then we will try to put Acceleron V up again.

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Splice test #3 - Sikaflex - Success

We did a successful burst test on the Sikaflex asymmetric splice with a PL attached sleeve. (splice #5) The bottle ends were also reinforced with a jacket made from another PET bottle and held down with glass strapping tape. We learned a couple of things from this test:

The Sikaflex works great as a sealant and the width of the sleeve was more than sufficient to hold the splice together.

The final burst pressure was 190 psi! This is a better result than was expected. The actual failure was due to the strapping tape breaking, weakening the bottle reinforcing and then ultimately bursting the bottle. The sleeve still held though. The normal burst pressure of these bottles is about 165 psi.


This is a photo of the splice under test. The needle on top of the bottle was added to see how much bottle distorts close to the sleeve.

I'll make up three of these splices next and see how reproduceable the results are. I won't be testing them to destruction but pushing them to 140 psi, for an operational pressure of 130psi in actual rockets. If the results can be replicated, it would give us a nice safety margin.

I do have good slow motion video of the bottle's distortion and ultimate burst. I'll post the video with the next main website update, as I am busy the next couple of nights getting ready for this weekend's launch event.
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Splice test #2 - Epoxy

After letting the epoxy splice sit for a week we pressure tested the spliced-pair to destruction today. At around 120 psi a small leak developed. We kept increasing the pressure until the splice failed at ~150psi.

This time it was the PET bottle that failed rather than the splice. It fairly cleanly tore itself off from around the edge of the sleeve. The epoxy glue though separated cleanly from the bottle that flew off. This means that the epoxy did not do as good a job of holding onto the PET, even though the 1cm x 1cm tests showed promising results.

The sleeve was glued on with PL premium.

We are now waiting for the sikaflex and PL to cure on the next splice test.

The reinforcing shells worked well and the bottles did not show any signs of stress in the neck area. We have taken them off again, and will use them on the next splice test.

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Bits and pieces

We've updated the main website with some of the things we've been working on over the last month or so:

http://home.people.net.au/~aircommand/day81.htm

The update includes discussion of the splice variants we are currently testing as well as details of my involvement in the rocket challenge on Channel 7's 'Beauty and the Geek - Australia'.

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Splice test 1

I tested the splice yesterday, but it sprung a leak at 130 psi, which was disappointing, but not unexpected for the first attempt. It was only 4 days since I did the splice so it may not have been quite long enough for a full cure of the splice. Except for the leak the splice held well though, and there were no stress marks on the bottles. All up the reinforced double-walled spliced pair was 3.15L and weighed 139 grams.

The reinforcing shells used on both ends of the rocket can be easily removed and reused for the next test since they are not glued, saving a couple of bottles there. They protected the inner bottles well during the test.

Having recently performed the 1cm x 1cm shear tests on the Araldite super strength epoxy, I've made a new splice using this glue last night, and it looks like it has a much better seal. It does not bubble up like the PL. I used very gentle heat from the heat gun to make it flow better into the corners once the splice was assembled. Tonight I'll add the extra outer sleeve and glue it on with PL.

If the epoxy fails, next I'll try the sikaflex on the inner splice for a better seal, and then again use PL for the outer sleeve.

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New Splices

We have been using the same symmetrical splice technique on our 2L bottles for a couple of years now, but I have never quite been happy with it. We have had quite a few failures along the way, and the no-leak yield hasn't been as high as we would like. This meant a lot of wasted bottles and wasted time. The other issue has been the relatively low pressures the spliced pairs could hold. 130psi has been the limit we could practically push them to.

We used to use 2.25L bottles as the sleeve since they fit well over the 2L bottles and no shrinking was required. But recently we have found that some of the 2.25L bottles don't fit as well as they used to so it has been difficult to use them as well. To try to stop the leaks we have been using a different glue to do the sealing in the joint and PL to hold the splice together but this made the process more complex and we still ended up with leaks although less often.

So we are currently trialing a different technique that will hopefully yield better results. The technique is not new but a combination of several different techniques used together. We are using just PL glue for this splice and only the one type of bottle. I'll post the full technique on the main site, but here is a quick run down:

We first heat shrink about 2-3 cm of one of the bottles using hot water so that it fits inside another bottle of the same type. Then curl the edge on a pan. This has the effect of giving a tight seal where the heat shrink section ends and meets the other bottle since they are the same diameter at this point. We sand and glue these sections together. We then make up a sleeve about 4 cm wide made out of the same type of bottle. Because the diameter is the same we simply cut the sleeve to turn it into a strip. We then use another section of sleeve about 4 x 4cm and glue half of it to the sleeve strip to cover the gap. We let the glue dry for a couple of days. Then we glue the sleeve strip over the splice to provide further strength to the splice.

The drawback is that inserting one bottle into the other means that the volume is smaller, but not by too much.

We have had to previously reinforce the necks of the bottles with rings made from other bottles, but it only strengthened the necks not the rest of the bottle. This time we are going to use Richard Wayman's bottle-on-bottle technique to not only strengthen the neck but a significant portion of the rest of the bottle.

Hopefully this technique will yield better sealing results and will be able to take higher pressures.

The glue is curing at the moment so tests will be carried out at the next opportunity.

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It's been a while since the last update because there has only been little rocket related development in the last two weeks.

Crestwood Fair and other stuff

Last Sunday I spent the whole day helping to man NSW rocketry association's stall at the Crestwood fair. David and Neville did a great job of organizing the stall and getting all the display materials together. We had all sorts of rockets on display, and I even brought along a couple of water rockets including the Acceleron V to sit in the corner. It was a fun day talking with people about rockets. Quite a few interested people stopped by for a chat. We gave out close to 50 fliers on the day, so we'll see how many people turn up to the next launch at Doonside.


Over the last two weeks there were also several birthday parties, accountants to see, kid's school concerts, and kids cricket games which meant a lot of time away from the rocket workshop. Now that the dust is settling down, we'll be back to more regular development. Dad is also back from Europe so we'll have more time to spent on developing the next set of rockets.

Work has also been continuing on the website extension. There is just a lot of typing to do, and it's taking a lot longer than I originally expected. There are around 70 pages on there so far.

New workshop
We had a long weekend this week, but instead of rockets I decided to concentrate my efforts on making significant progress on the new workshop under the house. The current workshop is just getting too small. Dad and I spent all three days putting up the internal walls, which I'm happy about, because those are done now and the ceiling is next. We had the electricians come in earlier in the week to put in all the power points and lighting, and we'll need them to come back to finish everything off after we have painted. There is probably 3 weeks or so more work on it, because we need to put in new doors, do the little trim bits to finish it off, and then fit it out with benches and shelving.

Coming up
Last week we've also made a booster for Paul's pyro rocket, so we are hoping to fly it this upcoming weekend if the weather improves. It will be our very first two stage pyro rocket launch.


We are bringing a couple of water rockets with us as well of course. We will fly the rocket with the camera mounted on the boom again to see if we can get a clearer view of the water behaviour in the rocket during flight. Acceleron V is currently slated to fly at the end of the month's NSWRA launch.
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A different perspective

We had a good flight day on Sunday at Doonside. Although the wind was fairly strong we managed to get 3 flights in.



The first flight was that of a modified rocket giving us a different perspective of the rocket. We were using the technique to investigate what happens inside the lowest bottle during flight. We mounted the camera on a long boom sticking out the side and looking back at the rocket and nozzle.

The full writeup with pictures and video of the flight is here:
http://www.AirCommandRockets.com/day80.htm

I want to fly this one again, but actually remember to put the food colouring in it this time for better contrast enhancement. The fins also need to be painted a darker colour to work better with the camera's auto-iris.
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Lots of progress, little time to write about it

Here is a quick update as there has been lots of stuff happening in the background but have had little time to do proper write ups on the main website.

Flight Computers
Flight computers V1.7 and 2.0 are coming along well. We are developing two different ones at the same time with different capabilities. V1.7 is aimed at providing a very simple, inexpensive and small solution to parachute deployment. Focus is on least number of components in a lightweight package coupled with a single 3.7g servo and a small 6V battery.

V2.0 is a more advanced version offering expanded functionality over V1.6, with extension modules that are also suitable for pyro rockets. V2.0 also offers a much more flexible programing model capable of sequencing complex operations.

One of the main design criteria for these flight computers is that they can be fully configured in the field without any special external equipment like keypads, displays or a laptop. Both are now using surface mount devices for smaller footprints.

Website Extension
A lot of writeup time has been spent doing work on the website extension. This is mostly why there has been fewer updates on the main site. Currently the plan is to go live with the extension at the end of September. Some of the recent write ups will be available with the extension.

Rocket development
Acceleron V is currently resting until dad gets back from Europe. I've gone and given it a bit of a service clean such as the non-return valve that was showing signs of corrosion, and generally made sure that everything was in order. We need to take two cars full of equipment to the launch site and it takes both of us to set it up and launch it, so it will wait until he gets back.

The new rocket I want to fly this weekend (Sunday) is also close to ready. I'm using the Acceleron launcher, (without boosters) as it already has provisions for the 2 meter guide rail, as the rocket design does not allow us to use our regular launcher.

Other projects
I've also been helping out with prototyping work for a paid rocket project which I can't post about yet, but it has been quite interesting and something different. This has also taken up quite a bit of my time over the last two weeks.

On top of that I am finally working again on the new bigger workshop under the house. I'm hoping the electrician will be able to come in this week for a quote for all the wiring, and then we can put up the wall panels and then it should start looking like a real workshop. :)

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How to make a nozzle tutorial

This weekend we've put together a couple of short video tutorials on how to make a 9mm Gardena nozzle. One of the issues that people have been reporting is that they are unable to get a hold of the older bottle caps with removable seals. The video covers an alternate source of caps that are suitable for making the nozzles:

http://www.youtube.com/watch?v=hiixdmrSEbA

The second video shows how to resolve an issue with some launchers as not all Gardena (and clones) quick connect fittings are created equal. The problem reported by quite a few people is that the nozzle does not lock all the way down into the launcher. The nozzle appears to be locked in position but releases itself as pressure builds. The solution is fairly simple:

http://www.youtube.com/watch?v=y56A9_sIelU


We did not attend the launch at Doonside this week because the weather predictions indicated strong wind and rain. When I woke up in the morning I saw that it was pouring, and decided to skip the hour long drive to the launch site. A number of people attended the launch but said the weather was less than ideal.

The good news is that NSWRA now has permission to launch 2 times a month at Doonside. So the wait time for doing bigger test flights is reduced.
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Acceleron Photos from 4th July

A big thanks goes to Andrew from NSWRA for shooting the following photos of the Acceleron V booster in flight. We didn't get any still photos of the launch on the day as we were busy shooting video. (click on the images for a higher res version)

In the first one you can see the turbulent flow from the red and blue nozzles, whereas the green nozzle has very nice laminar flow (seen further down the plume).

The second photo is my favorite one with the air pulse starting and the sun reflecting from the sustainer.

The last one shows the rocket shortly after staging occurred. The black fins of the sustainer are about to clear the nose of the booster.


I'll post some of the other photos of the flight in next main page update.

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Development continues

It's been a while since the last update so I thought I'd post about what we've been up to. In the last few weeks I've been catching up mostly on non-rocket related matters, but development has been progressing.

Acceleron Vc
The rocket is now mostly repaired. The broken ring brace was easily repaired with a bit of epoxy glue, and a new coat of paint. New separator rings have also been made and are currently having the servo and camera fitted. The only thing that needs to be done is for the whole rocket to be pressure tested again and re-assembled.

We are also making up a whole bunch of new spliced pairs of 2L bottles (we are processing about 40 bottles) to have spare ones ready in case some of the original pairs fail during testing. These will also be used for the Polaron rockets and new bigger boosters.

New rocket
We have also been building a new smaller rocket (not named yet) to try to better understand how foam and foam generation behaves during flight. This rocket was built small so that we can fly it at our local park. I'll post full details in the next main website update.

I've also been working on an extension to our website that hopefully will go live in the next month or two because there is still lots of information to enter and format.
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